The invention relates to an electrolysis cell having a housing provided with an inlet and an outlet for a throughflowing electrolyte, in which monopolar electrodes are disposed, each of them consisting of plates arranged parallel and fastened to a common support, the electrodes being offset from one another such that the plates of the one polarity extend into the interstices formed between the plates of the other polarity, and it relates also to the use thereof.
Electrolysis cells both of monopolar and of bipolar types of construction are used for the performance of chemical processes. The bipolar cell, which is constructed by placing bipolar electrodes in series in the manner of known filter presses, has the advantage that the leads carrying power to the outer electrodes can be made thinner than they can in a monopolar cell of the same power input, that an electrolysis installation constructed by the arrangement in series of a plurality of bipolar cells requires less space than the monopolar cell installation, and the construction of such an installation is simpler due to the elimination of the often complicated and expensive cell connectors. However, the bipolar cell also has a number of disadvantages with respect to a monopolar cell.
Furthermore, electrolysis cells of rectangular, square and circular cross section are known, in which the flow of the electrolyte can take place in any desired manner through appropriate pipe connection flanges, namely horizontally, meander-wise, diagonally or vertically. In general the vertical direction of flow of the electrolyte is to be preferred for hydrodynamic reasons, especially when short times of stay in the cell are necessary, or when use is to be made of the lifting effect of electrolytically produced gases on the basis of the principle of the air lift pump.
German Auslegeschrift 2,109,949 discloses an electrolysis system having cells arranged in series through which the electrolyte flows vertically, and in which laminated bipolar electrodes are disposed. The bipolar electrodes consist in this case of multi-layer laminated plates on both sides of which there are fastened a plurality of vertically projecting, flag-like or bridge-like electrode plates, those of the one polarity being on the one side and only those of the opposite polarity being on the other. The flag-like portions of the electrodes of the one polarity extend into the interstices formed by the flag-like portions of the electrode of the other polarity.
Lastly, Canadian Pat. No. 914,610 discloses an electrolysis cell of the initially described kind, through which the electrolyte flows from the bottom to the top in a horizontally meandering manner. A plurality of such cells can be combined by bolting them back to back to form an installation through whose individual cell chambers the electrolyte flows serially, parallel to the direction of flow, or parallelly, perpendicularly to the direction of flow.
For the input of power, the known cells have on the outside of the cell casing or on the outside of the electrode support plates, if the latter simultaneously form a wall of the cell casing, connecting surfaces or connecting lugs for each polarity, which are bolted or otherwise fastened to the power conductor of copper or aluminum.
In the electrolysis cells disclosed by the two patents named above, the support plate for the individual cathode plates forms a part of the trough-like cell casing or it is welded or bolted to the cell casing. In general, the cell casing, consisting of iron or titanium, is connected in an electrically conductive manner to the cathode, i.e., it is cathodically connected, while the anode is fastened so as to be electrically insulated from the cell casing and leakproof.
In the known electrolysis cells of monopolar design, the total current is carried directly to the support plate, which in some cases simultaneously forms the cell wall, and from thence it is uniformly distributed to the individual electrode plates fastened perpendicularly on the support plate. In a cell constructed, for example, for a power input of 6 kiloamperes (kA), which contains a support plate having eleven individual cathode plates fastened thereon and electrically at the same potential as the casing, as well as a titanium support plate with twelve individual anode plates fastened thereon and extending into the twelve cathode interstices formed by the eleven individual cathodes, thus forming electrolyte interstices each 4 mm wide, the total current is conducted through copper bus bars to the cathode support plate. 0.5 kA is fed to each individual electrode and a current of 6 kA flows from the anode support plate through copper bus bars to the next cell. Since the vertical length of the individual anode plates must not exceed 600 to 700 mm, since otherwise considerable losses of yield and power would result, the current input and the output of a cell cannot be increased simply by extending them in the vertical direction if the cell is to operate economically. On the other hand, on account of the relatively poor conductivity of the titanium usually used for the anodes, the horizontal length of the individual anode plates depends on their thickness; thus, for an individual anode 500 mm high and 200 mm wide, a metal thickness of 1 to 2 mm is required.
Thus, if it were desired, in the case of one of the known cells to double the power input by doubling the horizontal dimension, the metal thickness would have to be quadrupled, i.e., the metal thickness of the individual anode plate would have to be increased with the square of the current input. For practical and economic reasons, therefore, the known cells having opposite, electrode-bearing sidewalls are suitable for no more than a limited power input of, say, 10 kA.